Limiting access to a digital item

ABSTRACT

In a method for limiting access to a digital item, a count for the digital item is stored, wherein the count is a number of accesses permitted for the digital item. A password for accessing the digital item is received. A plurality of password hashes is generated by utilizing one-way hash functions based on the number of accesses of the count and the password to generate the plurality of password hashes based on the count. The plurality of password hashes is stored in a password hash file.

PRIORITY CLAIM AND RELATED APPLICATION

This patent application is a continuation-in-part of and claims the benefit of co-pending U.S. patent application Ser. No. 13/712,514, entitled “LIMITING ACCESS TO A DIGITAL ITEM,” filed on Dec. 12, 2012, invented by Uday Kurkure, and assigned to the assignee of the present application, the entirety of which is hereby incorporated by reference.

BACKGROUND

Various forms of digital items are subject to access controls. These digital items include, but are not limited to, virtual appliances operating on virtual machines, as well as applications, digital media, and digital documents. There are many reasons as to why this is advantageous. For instance, the owner of the digital item may wish to ensure the security of the digital item. Alternatively, the owner of the digital item may wish to ensure that they receive compensation for the use and/or access of the digital item. One way to control access to a digital item is to limit the number of accesses a user may be granted to the digital item.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate various embodiments and, together with the Description of Embodiments, serve to explain principles discussed below. The drawings referred to in this brief description of the drawings should not be understood as being drawn to scale unless specifically noted.

FIG. 1 is an example data flow diagram illustrating initialization of a process for limiting the number of accesses to a digital item, in accordance with embodiments.

FIG. 2 is an example data flow diagram illustrating validation of a process for limiting the number of accesses to a digital item, in accordance with embodiments.

FIG. 3 is an example data flow diagram illustrating updating the stored count and stored password hash in a process for limiting the number of accesses to a digital item, in accordance with embodiments.

FIG. 4 is an example data flow diagram illustrating the changing of a password in a process for limiting the number of accesses to a digital item, in accordance with embodiments.

FIG. 5A is a flow diagram of the initialization in a method of limiting the number of accesses to a digital item, in accordance with various embodiments.

FIGS. 5B, 5C and 5D are flow diagrams of the initialization of a method of limiting the number of accesses to a digital item in which a plurality of password hashes are generated and stored in a password hash file, in accordance with various embodiments.

FIG. 6 is a flow diagram of access validation in a method of limiting the number of accesses to a digital item, in accordance with various embodiments.

FIG. 7A is a flow diagram of the update of the stored count and stored password hash in a method of limiting the number of accesses to a digital item, in accordance with various embodiments.

FIG. 7B is a flow diagram of the update of the stored count and stored password hash in a method of limiting the number of accesses to a digital item in which a plurality of password hashes are generated and stored in a password hash file, in accordance with various embodiments.

FIG. 8 is a flow diagram of the change of a password in a method of limiting the number of accesses to a digital item, in accordance with various embodiments.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. While various embodiments are discussed herein, it will be understood that they are not intended to be limiting. On the contrary, the presented embodiments are intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope the various embodiments as defined by the appended claims. Furthermore, in this Description of Embodiments, numerous specific details are set forth in order to provide a thorough understanding. However, embodiments may be practiced without one or more of these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the described embodiments.

Notation and Nomenclature

Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present Description of Embodiments, discussions utilizing terms such as “storing,” “receiving,” “performing,” “accessing,” “validating,” “denying,” “granting,” “decrementing,” “incrementing,” “generating,” “taking,” “repeating,” “deleting,” or the like, often refer to the actions and processes of an electronic computing device or system, such as a virtual machine, among others. In some embodiments, the electronic computing device/system may be a portion of a distributed computing system. The electronic computing device/system transmits, receives, stores, manipulates and/or transforms signals represented as physical (electrical) quantities within the circuits, components, logic, and the like, of the electronic computing device/system into other signals similarly represented as physical electrical quantities within the electronic computing device/system or within or transmitted to other electronic computing devices/systems.

Overview of Discussion

In accordance with various described embodiments, one way to control access to a digital item is to limit the number of accesses a user may be granted to the digital item. These digital items include, but are not limited to, virtual appliances operating on virtual machines, virtual machines, as well as applications, digital media, and digital documents. Conventional techniques for limiting the number of accesses to a digital item are typically reliant on the security of the access system. For example, the number of permitted accesses to a particular digital item, referred to herein as the “count” or the “stored count” is typically stored in a file, referred to herein as an “access count file.” Circumventing conventional techniques for limiting the number of accesses to a digital item is as simple as modifying the count within the access count file. For example, if a user wants to gain more accesses to a digital item, increasing the number of the count will grant them additional accesses.

Systems for limiting the number of accesses to a digital item may be implemented locally or over a distributed computer network, e.g., deployed in a cloud computing environment. Moreover, these systems may be private or public. As such, certain users may be able to access these systems, and the respective access count files, depending on the security measures taken. For example, someone skilled in circumventing security systems of computer systems, such as a hacker, or someone granted extensive administrative privileges to a system, such as a superuser, can easily gain access to and modify the access count file.

Embodiments described herein relate to methods and systems for limiting access to a digital item. The described embodiments associate a one-way password hash and a count of the number of permitted accesses with the digital item. A one-way hash function is performed on the password based on the number of permitted accesses of the count. In one embodiment, at initialization and at each access, a password hash is generated using a one-way hash function and is stored. On granted accesses, the count is decremented and the password hash is updated based on the decremented count. At an access request, the same one-way hash function is performed on the entered password based on the count. If the result of the one-way operation on the entered password matches the stored password hash access is granted.

In another embodiment, the password hashes for multiple accesses to the digital item are pre-calculated. For example, the password hashes for all permitted access to the digital item are pre-calculated. In the present embodiment, at initialization, a plurality of password hashes is generated using a one-way hash function. The plurality of password hashes is stored in a password hash file. The plurality of password hashes is based on the number of permitted accesses of the count and includes the password hashes for multiple permitted accesses to the digital item. At an access request, the same one-way hash function is performed on the entered password based on the count. If the result of the one-way operation on the entered password matches the stored password hash access is granted. On granted accesses, the count is decremented and the stored password hash matching the access password hash is deleted from the password hash file.

Tampering with the count in an attempt to increase the number of accesses will not succeed in exceeding the number of accesses to the digital item. For example, if the count is modified, the one-way hash of the entered password will not match the stored password hash, since both are based on the stored count.

Herein various systems, methods and techniques for limiting the number of accesses to a digital item are described which utilize one-way hash function based on the number of permitted accesses to the digital item.

Discussion begins with a description of flow diagrams illustrating portions of a process for limiting the number of accesses to a digital item. Operation of various components of a system for limiting the number of accesses to a digital item is further described in conjunction with description of various methods associated with limiting the number of accesses to a digital item.

Example Flow Diagrams for Limiting the Number of Accesses to a Digital Item

FIG. 1 is an example data flow diagram 100 illustrating initialization of a process for limiting the number of accesses to a digital item, in accordance with various embodiments. As depicted, access count file 110 includes the count of the number permitted accesses for a digital item. It should be appreciated that the count of permitted accesses can be stored in different ways, and is not limited to storage in an access count file 110. Moreover, it should be appreciated that access count file 110 can be stored locally or remotely, e.g., in a cloud computing environment.

At initialization, a password 105 for accessing a particular digital item is received. In one embodiment, password 105 is associated with a particular user, e.g., as identified by a username. In one embodiment, a Lightweight Directory Access Protocol (LDAP) server is implemented for handling password hash storage and validation. For instance, Active Directory (AD) utilizing LDAP may be used.

One-way hash function 120 receives password 105 and receives stored count 115 from access count file 110. In one embodiment, a user is supplied with password 105. In another embodiment, a user selects password 105. It should be appreciated that in various embodiments, password 105 is not stored, but rather a hash of password 105 (e.g., password hash 135) is stored. In one embodiment, password 105 is provided as input from a user, e.g., received at a keyboard or touchscreen device. In another embodiment, password 105 is stored on a device (e.g., a magnetic card or thumb drive) and is read by a corresponding input device (e.g., a magnetic card reader or computing system).

One-way hash function 120 is configured to perform a one-way hash function on password 105 based on the number of the stored count. For purposes of the instant description of embodiments, a one-way hash function refers to an operation that converts input text into an output string, referred to as a hash, but is computationally very difficult to retrieve or compute the input text from the output string. Moreover, one-way hash functions may also have the properties whereby it is infeasible to generate a particular hash without knowing both the input and the type of hash function being utilized and it is infeasible to modify the input text without changing the hash. Many different one-way hash functions are known to those of skill in the art. For example, and without limitation, some one-way hash functions include: MD2, MD4, MD5, RIPEMD, RIPEMD-128, RIPEMD-160, RIPEMD-256, RIPEMD-320, SHA-0, SHA-1, SHA-2, SHA-3, SHA-224, SHA-256, SHA-384, and SHA-512.

In the following example, one-way hash function SHA-256 is used generate hash values for the inputs “10” and “100.” Note that the hash values for 10 and 100 are very different. It is also very difficult to determine the original values of 10 and 100 from their hashes.

-   -   SHA256(“10”)=0x917df3320d778ddbaa5c5c7742bc4046bf803c36ed2b05         0f30844ed206783469     -   SHA256(“100”)=0xd98fad9074a4b77614bd8b62a73a7dff5928dd0e4a412         3400762ed10af19cd92

In one embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times corresponding to the number of stored count 115. For example, where n accesses to the digital item remain, such that the value of stored count 115 is n, one-way hash function 120 performs a one-way hash function on password 105 n number of times. That is, one-way hash function 120 would perform a one-way hash function on password 105 to generate an intermediate password hash. In one embodiment, one-way hash function 120 would perform the one-way hash function on successive intermediate password hashes until the one-way hash function has been performed n number of times.

In one embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times corresponding to the number of stored count 115 and at least one time less than the number of times corresponding to the number of stored count 115. For example, where n accesses to the digital item remain, such that the value of stored count 115 is n, one-way hash function 120 performs a one-way hash function on password 105 <n, n−1, . . . , 1> number of times. Each of these resulting password hashes can be stored to password hash file 130.

In one embodiment, one-way hash function 120 would perform the one-way hash function on successive intermediate password hashes until the one-way hash function has been performed n number of times, storing the resulting password hash 135 to password hash file 130. One-way hash function 120 would then perform the one-way hash function on successive intermediate password hashes until the one-way hash function has been performed n−1 number of times, storing the resulting password hash 135 to password hash file 130. In one embodiment, one-way hash function 120 would then perform the one-way hash function on successive intermediate password hashes until the password hash for all permitted accesses to the digital item. For example, where n=5, the one-way hash function is performed for all integers from one through five, and each resulting password hash is stored to password file 130 (e.g., five password hashes are stored in password hash file 130).

In another embodiment, one-way hash function 120 would perform a one-way hash function on password 105 to generate an intermediate password hash which is stored in password hash file 130. In one embodiment, one-way hash function 120 would perform the one-way hash function on successive intermediate password hashes until the one-way hash function has been performed n number of times, storing each of the intermediate password hashes to password hash file 130. For example, where n=5, one-way hash function 120 performs one one-way hash function on password 105 and stores the result to password hash file 130, then performs a one-way hash function on the result, storing each successive result, until five one-way hash functions have been performed.

In one embodiment, one-way hash function 120 performs a one-way hash function on password 105 using the same one-way hash function. In another embodiment, one-way hash function 120 performs a one-way hash function on password 105 using a combination of different one-way has functions. In one embodiment, one-way hash function 120 can cycle through a predetermined order of different one-way hash functions. One-way hash function 120 can maintain a list of various one-way hash functions, such that where multiple one-way hash functions are used based on the count, the one-way hash functions of the list are cycled through according to the number of stored count 115. For example, where the stored count 115 is five, and one-way hash function 120 performs five one-way hash functions on a password 105, each successive one-way hash function can be different. For example, all odd one-way hash functions can use SHA-256 and all even one-way hash functions can use SHA-384. It should be appreciated that any ordering of one-way hash functions can be used in accordance with the described embodiments, so long as the same ordering of one-way hash functions is used to validate access to the item, as described below in accordance with FIG. 2.

It should be appreciated that the one-way hash function can be performed on password 105 in other ways, and is not limited to the preceding embodiment. For example, in another embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times corresponding to a multiple of the number of stored count 115. In another embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times corresponding to an offset of the number of stored count 115. In other words, while the one-way hash function is performed on password 105 a number of times based on the number of stored count 115, it is not limited to being performed the number of times of stored count 115. In contrast, embodiments perform the one-way hash function on password 105 a number of times based on the number of stored count 115.

As depicted, password hash 135 includes the output of one-way hash function 120 after a one-way hash function has been performed on password 105 count number of times. In one embodiment, password hash 135 is stored in password hash file 130. It should be appreciated that password hash 135 can be stored in different ways, and is not limited to storage in password hash file 130. Moreover, it should be appreciated that password hash file 130 can be stored locally or remotely, e.g., in a cloud computing environment. In various embodiments, password hash file can include any number of password hashes 135.

Furthermore, as depicted in FIG. 1, in various embodiments, access count file 110 and password hash file 130 can be comprised within a single file, such as file 150. However, it should be appreciated that access count file 110 and password hash file 130 need not be comprised within the same file 150. For instance, having them in different files and at different locations might provide better security. It should also be appreciated that access count file 110, password hash file 130, and file 150 can be stored in different ways, and can be stored locally or remotely, e.g., in a cloud computing environment.

FIG. 2 is an example data flow diagram 200 illustrating validation in a process for limiting the number of accesses to a digital item, in accordance with various embodiments. As depicted, password 105 is received as part of an access request for a particular digital item. In one embodiment, password 105 is provided as input from a user, e.g., received at a keyboard or touchscreen device. In another embodiment, password 105 is stored on a device (e.g., a magnetic card or thumb drive) and is read by a corresponding input device (e.g., a magnetic card reader or computing system).

One-way hash function 120 receives password 105 and receives stored count 115 from access count file 110. One-way hash function 120 is configured to perform a one-way hash function on password 105 based on the number of the stored count. Access password hash 210 is generated by performing the one-way hash function based on the stored count 115. In one embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times equal to the number of stored count 115. In another embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times equal to a multiple of the number of stored count 115. In another embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times equal to an offset of the number of stored count 115. It should be appreciated that one-way hash function 120 performs the one-way hash function on password 105 in the same way as stored password hash 135 was generated.

In one embodiment, one-way hash function 120 performs a one-way hash function on password 105 using the same one-way hash function. In another embodiment, one-way hash function 120 performs a one-way hash function on password 105 using a combination of different one-way has functions. In one embodiment, one-way hash function 120 can cycle through a predetermined order of different one-way hash functions. One-way hash function 120 can maintain a list of various one-way hash functions, such that where multiple one-way hash functions are used based on the count, the one-way hash functions of the list are cycled through according to the number of stored count 115. It should be appreciated that any ordering of one-way hash functions can be used in accordance with the described embodiments, so long as the same ordering used in validating access to the item is used in the generation of stored password hash 135.

As depicted, access password hash 210 includes the output of one-way hash function 120 after a one-way hash function has been performed on password 105 based on the number of stored count 115.

In one embodiment, access validator 220 receives access password hash 210 and stored password hash 135. Access validator 220 compares access password hash 210 to stored password hash 135. If access password hash 210 and stored password hash 135 are not the same, access to the digital item is denied. Alternatively, if access password hash 210 and stored password hash 135 are equal, access to the digital item is granted. It should be understood that if the count in access count file 110 is tampered with, the access password 105 will be hashed an incorrect number of times and access password hash 210 will not match the stored password hash 135. Thus, tampering with the count does not succeed in gaining unauthorized access.

In another embodiment, access validator 220 receives access password hash 210 and a plurality of stored password hashes 135 stored in password hash file 130. Access validator 220 compares access password hash 210 to the plurality of stored password hashes 135. If the plurality of stored password hashes 135 does not include access password hash 210, access to the digital item is denied. Alternatively, the plurality of stored password hashes 135 does include access password hash 210, access to the digital item is denied, access to the digital item is granted. It should be understood that if the count in access count file 110 is tampered with, the access password 105 will be hashed an incorrect number of times and access password hash 210 will not match any of the plurality of stored password hashes 135. Thus, tampering with the count does not succeed in gaining unauthorized access

FIG. 3 is an example data flow diagram 300 illustrating updating the stored count and stored password hash in a process for limiting the number of accesses to a digital item, in accordance with embodiments. As depicted, responsive to access being granted to the digital item, access count 110 is decremented. For example, where the value of stored count 115 is n, the value of stored count 115 is updated to n−1. In one embodiment, access validator 220 decrements stored count 115 upon granting access, as shown at arrow 310.

In one embodiment, one-way hash function 120 then performs a one-way hash function on password 105 n−1 number of times, which is the value of stored count 115. Password hash 135 is generated by one-way hash function 120 and is stored in password hash file 130, replacing the previous password hash 135. In this way, access count file 110 and password hash file 130 or, in another embodiment, file 150, are updated to reflect that the remaining available accesses for the digital item is reflected as stored count 115 and that password hash 135 corresponds to stored count 115. In one embodiment, prior to replacing the previous password hash 135, the new password hash 135 is committed to persistent memory and is confirmed accessible. Once the new password hash 135 is confirmed accessible, the previous password hash 135 is deleted and replaced with the new password hash 135.

In another embodiment, where password hash file 130 includes a plurality of password hashes 135, responsive to access being granted to the digital item, the stored password hash that matches access password hash (e.g., access password hash 210 of FIG. 2) is deleted from password hash file 130.

FIG. 4 is an example data flow diagram 400 illustrating the changing of a password in a process for limiting the number of accesses to a digital item, in accordance with various embodiments. In the event that a password for accessing a digital item is changed, the corresponding password hash is updated to ensure that access to the digital item is maintained.

In accordance with various embodiments, password updater 410 receives an indication that password 105 has changed. It should be appreciated that the mechanism for verifying and performing the password change is managed separately, for instance, at an LDAP server or by AD. Password updater 410 receives the indication of the change, as well as the changed password 105.

One-way hash function 120 receives password 105 and receives stored count 115 from access count file 110. One-way hash function 120 is configured to perform a one-way hash function on password 105 based on the number of the stored count. In one embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times corresponding to the number of stored count 115.

It should be appreciated that the one-way hash function can be performed on password 105 in other ways, and is not limited to the preceding embodiment. For example, in another embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times corresponding to a multiple of the number of stored count 115. In another embodiment, one-way hash function 120 performs a one-way hash function on password 105 a number of times corresponding to an offset of the number of stored count 115. In other words, while the one-way hash function is performed on password 105 a number of times based on the number of stored count 115, it is not limited to being performed the number of times of stored count 115. In contrast, embodiments perform the one-way hash function on password 105 a number of times based on the number of stored count 115.

As depicted, password hash 135 includes the output of one-way hash function 120 after a one-way hash function has been performed on password 105 count number of times. In one embodiment, the updated password hash 135 is stored in password hash file 130, replacing the previous password hash 135. It should be appreciated that where password hash file 130 includes a plurality of password hashes 135, each password hash 135 can be updated in accordance with the changing of a password in a process for limiting the number of accesses to a digital item illustrated by data flow diagram 400.

Example Methods of Operation

The following discussion sets forth in detail the operation of some example methods of operation of embodiments. With reference to FIGS. 5A through 8, flow diagram 500, 550, 580, 590, 600, 700, 780 and 800 illustrate example procedures used by various embodiments. Flow diagrams 500, 550, 580, 590, 600, 700, 780 and 800 include some procedures that, in various embodiments, are carried out by a processor under the control of computer-readable and computer-executable instructions. In this fashion, procedures described herein and in conjunction with flow diagrams 500, 550, 580, 590, 600, 700, 780 and/or 800 are, or may be, implemented using a computer, in various embodiments. The computer-readable and computer-executable instructions, e.g., computer readable program code, can reside in any tangible computer readable storage media. Some non-limiting examples of tangible computer readable storage media include random access memory, read only memory, magnetic disks, solid state drives/“disks,” and optical disks, any or all of which may be employed. The computer-readable and computer-executable instructions, which reside on tangible computer readable storage media, are used to control or operate in conjunction with, for example, one or some combination of processors of a computing system. It is appreciated that the processor(s) may be physical or virtual or some combination (it should also be appreciated that a virtual processor is implemented on physical hardware).

Although specific procedures are disclosed in flow diagrams 500, 550, 580, 590, 600, 700, 780 and 800, such procedures are examples. That is, embodiments are well suited to performing various other procedures or variations of the procedures recited in flow diagram 500, 550, 580, 590, 600, 700, 780 and/or 800. Likewise, in some embodiments, the procedures in flow diagrams 500, 550, 580, 590, 600, 700, 780 and/or 800 may be performed in an order different than presented and/or not all of the procedures described in one or more of these flow diagrams may be performed. It is further appreciated that procedures described in flow diagram 500, 550, 580, 590, 600, 700, 780 and/or 800 may be implemented in hardware, or a combination of hardware with firmware and/or software.

FIG. 5A is a flow diagram 500 of the initialization of a method of limiting the number of accesses to a digital item, in accordance with various embodiments. It should be appreciated that digital items may include, but are not limited to, virtual appliances operating on virtual machines, virtual machines, as well as applications, digital media, and digital documents.

At procedure 510 of flow diagram 500, in one embodiment, a count for the digital item is stored, wherein the count is a number of accesses permitted for the digital item. In one embodiment, the count is stored in an access count file, e.g., access count file 110 of FIG. 1.

At procedure 520, a password for accessing the digital item is received. In one embodiment, the password is associated with a particular user, e.g., as identified by a username. In one embodiment, the password is provided as input from a user, e.g., received at a keyboard or touchscreen device. In another embodiment, the password is stored on a device (e.g., a magnetic card or thumb drive) and is read by a corresponding input device (e.g., a magnetic card reader or computing system).

At procedure 530, a one-way hash function is performed on the password based on the number of accesses of the count to generate a password hash based on the count. In one embodiment, as shown at procedure 532, the one-way hash function is performed on the password the number of the count times. In another embodiment, as shown at procedure 534, the one-way hash function is performed on the password a multiple of the number of the count times. In another embodiment, as shown at procedure 536, the one-way hash function is performed on the password an offset of the number of the count times.

At procedure 540, the password hash is stored as the stored password hash.

FIGS. 5B, 5C and 5D are flow diagrams 550, 580 and 590, respectively, of the initialization of a method of limiting the number of accesses to a digital item in which a plurality of password hashes are generated and stored in a password hash file, in accordance with various embodiments. It should be appreciated that digital items may include, but are not limited to, virtual appliances operating on virtual machines, virtual machines, as well as applications, digital media, and digital documents.

At procedure 562 of flow diagram 550, in one embodiment, a count for the digital item is stored, wherein the count is a number of accesses permitted for the digital item. In one embodiment, the count is stored in an access count file, e.g., access count file 110 of FIG. 1.

At procedure 564, a password for accessing the digital item is received. In one embodiment, the password is associated with a particular user, e.g., as identified by a username. In one embodiment, the password is provided as input from a user, e.g., received at a keyboard or touchscreen device. In another embodiment, the password is stored on a device (e.g., a magnetic card or thumb drive) and is read by a corresponding input device (e.g., a magnetic card reader or computing system).

At procedure 566, a plurality of password hashes is generated by utilizing one-way hash functions based on the number of accesses of the count and the password to generate the plurality of password hashes based on the count. In one embodiment, as shown at procedure 568, generating the plurality of password includes iteratively generating the plurality of password hashes by performing the one-way hash function on the password the number of the count times and performing the one-way hash function on the password at least one decremented number of the count times.

In another embodiment, generating the plurality of password hashes of procedure 566 is performed as shown at flow diagram 580 of FIG. 5C. At procedure 582 of flow diagram 580, a one-way hash function is performed on the password based on the number of accesses of the count to generate a password hash based on the count. At procedure 584, the count is decremented to update the count with a decremented count. At procedure 586, it is determined whether the count indicates that access is permitted to the digital item (e.g., the count is not equal to zero). If the count indicates that access is permitted to the digital item, procedures 582 and 584 are repeated. In one embodiment, as shown at procedure 588, procedures 582 and 584 are repeated until the count indicates that access is not permitted to the digital item.

In another embodiment, generating the plurality of password hashes of procedure 566 is performed as shown at flow diagram 590 of FIG. 5D. At procedure 592 of flow diagram 590, a one-way hash function is performed on the password based on the number of remaining accesses to generate a password hash based on the count. It should be appreciated that at the first instance of procedure 592, the value indicating the fewest available remaining accesses (e.g., one remaining access) is used. At procedure 594, the remaining accesses to the digital item is incremented. At procedure 596, it is determined whether the remaining accesses exceed the count. If the remaining accesses does not exceed the count, procedures 592 and 594 are repeated. In one embodiment, as shown at procedure 598, procedures 592 and 594 are repeated until the remaining accesses exceed the count.

Returning to FIG. 5B, at procedure 570, the plurality of password hashes is stored in the password hash file. It should be appreciated that the intermediate results of the performing the one-way hash function on the password, as described in accordance with flow diagrams 580 and 590, are stored as the plurality of password hashes in the password hash file.

FIG. 6 is a flow diagram 600 of access validation in a method of limiting the number of accesses to a digital item, in accordance with various embodiments.

At procedure 610 of flow diagram 600, in one embodiment, a request to access the digital item is received, the request including the password. In one embodiment, the password is provided as input from a user, e.g., received at a keyboard or touchscreen device. In another embodiment, the password is stored on a device (e.g., a magnetic card or thumb drive) and is read by a corresponding input device (e.g., a magnetic card reader or computing system).

At procedure 620, the count for the digital item is accessed.

At procedure 630, a one-way hash function is performed on the password based on the number of accesses of the count to generate an access password hash based on the count. It should be appreciated that the one-way hash function can be performed in different ways, so long as the one-way hash function is based on the count and is performed in the same manner as described in procedure 530 of FIG. 5.

At procedure 640, the request is validated by comparing the stored password hash to the access password hash. As shown at procedure 642, it is determined whether the stored password hash matches the access password hash.

If the stored password hash does not match the access password hash, as shown at procedure 650, access to the digital item is denied. Alternatively, if the stored password hash matches the access password hash, as shown at procedure 652, access to the digital item is granted. In one embodiment, flow diagram 600 proceeds to procedure 710 of flow diagram 700.

FIG. 7A is a flow diagram 700 of the update of the stored count and stored password hash in a method of limiting the number of accesses to a digital item, in accordance with various embodiments. It should be appreciated that in accordance with various embodiments, flow diagram 700 is performed responsive to granting access to a digital item.

At procedure 710 of flow diagram 700, the count is decremented to generate a decremented count. For example, where the value of stored count 115 is n, the value of stored count 115 is updated to n−1.

At procedure 720, the decremented count is stored as the count.

At procedure 730, the one-way hash function is performed on the password based on the number of accesses of the count to generate an updated password hash based on the decremented count.

At procedure 740, the updated password hash is stored as the stored password hash.

In one embodiment, as shown at procedure 750, it is determined whether the count is decremented to a value indicating the access to the digital item is not available.

If it is determined that the count is not decremented to a value indicating the access to the digital item is not available, as shown at procedure 760, no action is taken.

If it is determined that the count is decremented to a value indicating the access to the digital item is not available, as shown at procedure 770, an indication that access to the digital item is denied is stored. In one embodiment, as shown at procedure 772, a random hash is generated. At procedure 774, the random hash is stored as the password hash.

FIG. 7B is a flow diagram 780 of the update of the stored count and stored password hash in a method of limiting the number of accesses to a digital item, in accordance with various embodiments. It should be appreciated that in accordance with various embodiments, flow diagram 780 is performed responsive to granting access to a digital item in which the password hash file (e.g., password hash file 130 of FIGS. 1-4) stores a plurality of password hashes.

At procedure 710 of flow diagram 700, the count is decremented to generate a decremented count. For example, where the value of stored count 115 is n, the value of stored count 115 is updated to n−1.

At procedure 720, the decremented count is stored as the count.

At procedure 790, the stored password hash of the plurality of password hashes of matching the access password hash is deleted from the password hash file.

In one embodiment, as shown at procedure 750, it is determined whether the count is decremented to a value indicating the access to the digital item is not available.

If it is determined that the count is not decremented to a value indicating the access to the digital item is not available, as shown at procedure 760, no action is taken.

If it is determined that the count is decremented to a value indicating the access to the digital item is not available, as shown at procedure 770, an indication that access to the digital item is denied is stored. In one embodiment, as shown at procedure 772, a random hash is generated. At procedure 792, the random hash is stored in the password hash file.

FIG. 8 is a flow diagram 800 of the change of a password in a method of limiting the number of accesses to a digital item, in accordance with various embodiments.

At procedure 810 of flow diagram 800, responsive to receiving an indication that the password has changed to an updated password, the one-way hash function is performed on the updated password based on the number of accesses of the count to generate an updated password hash based on the count.

At procedure 820, the updated password hash is stored as the stored password hash.

While various embodiments describe herein refer to the access of digital items, it should be appreciated that other embodiments are envisioned that are directed towards the access of physical items. For instance, the described systems and methods can be used to control access to physical items by limiting how many times the physical item can be accessed. By way of non-limiting example, a digital lock implementing the described embodiments can be used to limit access to physical items, such as a bank vault, a safe, a room, a house, etc.

In another example, a gaming system in an arcade may be protected by limiting access to a number of prepaid plays. Rather than using money or tokens in the gaming system directly, a password is provided. Each time the gaming system is played, the user enters the password. The gaming system employs the described embodiments to limit the number of plays (e.g., accesses) of the gaming system. In another example, rides on a motorized transport (e.g., a bus, a subway, or a theme park ride) are controlled according to the described embodiment. The user procures a particular number of rides and receives a password. The access to rides is limited to the number of rides the user buys. In one embodiment, the password is stored on a device, e.g., a magnetic card, that can be read by a corresponding device.

Example embodiments of the subject matter are thus described. Although various embodiments of the have been described in a language specific to structural features and/or methodological acts, it is to be understood that the appended claims are not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims and their equivalents. 

What is claimed is:
 1. A computer-implemented method for limiting access to a digital item, the method comprising: storing a count for the digital item, wherein the count is a number of accesses permitted for the digital item; receiving a password for accessing the digital item; generating a plurality of password hashes by utilizing one-way hash functions based on the number of accesses of the count and the password to generate the plurality of password hashes based on the count; and storing the plurality of password hashes in a password hash file.
 2. The computer-implemented method of claim 1, wherein the generating a plurality of password hashes comprises: iteratively generating the plurality of password hashes by performing the one-way hash function on the password the number of the count times and performing the one-way hash function on the password at least one decremented number of the count times.
 3. The computer-implemented method of claim 1, wherein the generating a plurality of password hashes comprises: performing a one-way hash function on the password based on the number of accesses of the count to generate a password hash based on the count; decrementing the count to update the count with a decremented count; and provided the count indicates that access is permitted to the digital item, repeating the performing the one-way hash function on the password and the decrementing the count; wherein intermediate results of the performing the one-way hash function on the password are stored as the plurality of password hashes in a password hash file.
 4. The computer-implemented method of claim 3, wherein the generating a plurality of password hashes further comprises: repeating the performing the one-way hash function on the password and the decrementing the count until the count indicates that access is not permitted to the digital item.
 5. The computer-implemented method of claim 1, wherein the generating a plurality of password hashes comprises: performing a one-way hash function on the password based on one remaining access to the digital item to generate a password hash; incrementing the remaining accesses to the digital item; and provided the remaining accesses does not exceed the count, performing a one-way hash function on the password based on the remaining accesses to the digital item to generate a password hash; wherein intermediate results of the performing the one-way hash function on the password are stored as the plurality of password hashes in a password hash file.
 6. The computer-implemented method of claim 5, wherein the generating a plurality of password hashes further comprises: repeating the performing the one-way hash function on the password and the incrementing the remaining accesses until the remaining accesses exceeds the count.
 7. The computer-implemented method of claim 1, further comprising: receiving a request to access the digital item, the request comprising the password; accessing the count for the digital item; performing the one-way hash function on the password based on the number of accesses of the count to generate an access password hash based on the count; and validating the request by comparing the plurality of stored password hashes to the access password hash.
 8. The computer-implemented method of claim 7, wherein the validating the request comprises: provided a stored password hash of the password hash file matches the access password hash, granting access to the digital item.
 9. The computer-implemented method of claim 8 further comprising: responsive to the granting access to the digital item: decrementing the count to generate a decremented count; storing the decremented count as the count; and deleting the stored password hash matching the access password hash from the password hash file.
 10. The computer-implemented method of claim 9 further comprising: provided all of the plurality of password hashes are deleted from the password hash file, storing an indication in the password hash file that access to the digital item is denied.
 11. The computer-implemented method of claim 10, wherein the storing an indication that access to the digital item is denied comprises: generating a random hash; and storing the random hash in the password hash file.
 12. A non-transitory computer readable storage medium having computer readable program code stored thereon for causing a computer system to perform a method for granting access to a digital item having a limited number of accesses, the method comprising: receiving a request to access the digital item, the request comprising a password; accessing a stored count for the digital item, wherein the stored count is a number of accesses permitted for the digital item; performing a one-way hash function on the password based on the number of accesses of the stored count to generate an access password hash based on the stored count; and validating the request by comparing a plurality of stored password hashes in a password hash file to the access password hash.
 13. The computer readable storage medium of claim 12, wherein the validating the request comprises: provided a stored password hash matches the access password hash of the plurality of stored password hashes matches the access password hash, granting access to the digital item.
 14. The computer readable storage medium of claim 13, wherein the method further comprises: responsive to the granting access to the digital item, deleting the stored password hash matching the access password hash from the password hash file.
 15. The computer readable storage medium of claim 14, wherein the method further comprises: provided all of the plurality of stored password hashes are deleted from the password hash file, storing an indication in the password hash file that access to the digital item is denied.
 16. The computer readable storage medium of claim 15, wherein the storing an indication that access to the digital item is denied comprises: generating a random hash; and storing the random hash in the password hash file.
 17. A computer-implemented method for limiting access to an item, the method comprising: storing a count for the item, wherein the count is a number of accesses permitted for the item; receiving a password for accessing the item; generating a plurality of password hashes by utilizing one-way hash functions based on the number of accesses of the count and the password to generate the plurality of password hashes based on the count; storing the plurality of password hashes in a password hash file; and responsive to granting access to the item: decrementing the count to generate a decremented count; storing the decremented count as the count; and deleting a stored password hash matching an access password hash from the password hash file.
 18. The computer-implemented method of claim 17 further comprising validating a request to access the item prior to the granting access to the item, the validating the request to access the item comprising: receiving the request to access the item, the request comprising the password; accessing the count for the item; performing the one-way hash function on the password based on the number of accesses of the count to generate an access password hash based on the count; and validating the request by comparing the plurality of password hashes to the access password hash, wherein provided a stored password hash of the plurality of password hashes matches the access password hash, access is granted to the item.
 19. The computer-implemented method of claim 17, wherein the generating a plurality of password hashes comprises: performing a one-way hash function on the password based on the number of accesses of the count to generate a password hash based on the count; decrementing the count to update the count with a decremented count; provided the count indicates that access is permitted to the item, repeating the performing the one-way hash function on the password and the decrementing the count; and repeating the performing the one-way hash function on the password and the decrementing the count until the count indicates that access is not permitted to the item; wherein intermediate results of the performing the one-way hash function on the password are stored as the plurality of password hashes in a password hash file.
 20. The computer-implemented method of claim 17, wherein the generating a plurality of password hashes comprises: performing a one-way hash function on the password based on one remaining access to the item to generate a password hash; incrementing the remaining accesses to the item; provided the remaining accesses does not exceed the count, performing a one-way hash function on the password based on the remaining accesses to the item to generate a password hash; and repeating the performing the one-way hash function on the password and the incrementing the remaining accesses until the remaining accesses exceeds the count wherein intermediate results of the performing the one-way hash function on the password are stored as the plurality of password hashes in a password hash file. 